Grinding wheel



Patented Feb. 10, 1942 GRINDING WHEEL Samuel S. Kistler, West Boylston,Mass, assignor to Norton Company, Worcester, Mass, a corporation ofMassachusetts No Drawing. Application August 2, 1941,

Serial No. 405,243

8 Claims.

The invention relates to grinding wheels and other abrasive bodiesbonded with organic bond.

One object of the invention is to provide an improved dry snaggingwheel. Another object of the invention is to provide a grinding wheel orother abrasive body which, in various embodiments, may be substitutedfor abrasive bodies bonded with shellac, rubber, or phenol formaldehyde,and which will remove a greater amount of metal for a given wheel wear.

Another object of the invention is to provide a resin bond for themanufacture of grinding wheels and other abrasive bodies having achemical reaction with the work piece to increase the abrading action.Another object of the invention is to provide an ingredient for additionto an aromatic amine-aldehyde polymer which causes adidtional curingthereof when heated.

Another object of the invention is to improve an aniline formaldehydepolymer. Another object of the invention is to improve an anilineformaldehyde bonded grinding wheel or other abrasive body.

Another object of the invention is to get an acid to the surface of thework piece being ground without spreading it all over the work piece,

thereby increasing the effectiveness of the grinding operation withoutetching the work piece or causing it to rust or otherwise detrimentallyaffecting it and without such disadvantages as spraying acid upon theoperator, upon the grinding machine, or corroding the coolant pipes orcoolant pump. Other objects will be in part obvious or in part pointedout hereinafter.

The invention accordingly consists in the features of construction,combinations of elements,

arrangements of atoms, and in the several steps and relation and orderof each of said steps to one or more of the others thereof, all as willbe illustratively described herein, and the scope of the application ofwhich will be indicated in the following claims.

I provide a quantity of abrasive grain, a quantity of a primary aromaticamine, .a quantity of aldehyde, and a quantity of an aromatic aminedi-hydrohalide, the halogen being selected from the group consisting ofchlorine, bromine and iodine. The latter substances react with thepolymer of the aromatic amine and aldehyde. According to the presentinvention I take aniline or other aromatic amine and formaldehyde orother aldehyde and condense them in the presence of a strong acid, andthen I modify the condensate with an aromatic amine di-hydrohalide.Preferably I first produce a polymer from the reaction of one molecularproportion of aniline with between one and three molecular proportionsof formaldehyde in the presence of at least approximately one molecularproportion of an acid at least as strong as phosphoric acid. The polymerthus formed is powdered.

I now take a quantity of abrasive grains, plasticize it with furfural,for example, then add the aniline formaldehyde polymer together with aquantity of an aromatic amine di-hydrohalide, for example,paraphenylene-diamine di-hydrochloride. I preferably mix the foregoingin a mixing machine until each granule is coated with the powderedconstituents, thus producing what is called a dry granular mix. Fromthis mixture I mold an abrasive body, press and heat the whole to atemperature capable of causing further reaction and suflicient to fusethe aniline formaldehyde resin. I can use any temperature from C. to C.inclusive with satisfactory results, and very likely temperaturesoutside of this range will give a satisfactory product.

While the preferred aromatic amine is aniline, I may use other primaryaromatic amines, such as metaphenylene diamine, metatoluidine anddiamino diphenyl methane. The preferred aldehyde used in my invention isformaldehyde and so far as I know this gives .better results than otheraldehydes. Secondly, however, I may use furfural to prepare the aromaticamine resin. A distinction must be made between a furfural aromaticamine resin, as such, and an abrasive body the abrasive grains of whichwere plasticized with furfural and the bond of which is I findmodifiedaromatic amine formaldehyde. that as a practical matter to facilitatethe use of "the dry granular mix method of making abrasive articles andalso for hot pressing, it is quite desirable to plasticize the abrasivegrains with furfural. During the curing reaction furyl methylene groupsattach themselves to the benzene rings of the resin, linking the ringstogether and increasing the strength of the resin, when furfural isadded at this stage. However, within the scope of the invention, theamine-aldehyde resin with abrasive grains and aromatic aminedihydrohalide may be hot pressed and furfural may be dispensed with.Also it is practical to use other liquid plasticizers.

The invention contemplates the use of any type of abrasive graindesired, for example, fused alumina and other kinds of alumina such asemery or corundum, silicon carbide or other hard carbide, quartz, ordiamonds.

Aniline, 7

in the presence of a strong acid, reacts with formaldehyde, HCHO,toproduce a long chain polymer which, when an excess of formaldehyde abovethe stoichiometric proportions is used, for

example, 20% excess of formaldehyde, has adjacent chains connected withmethylene groups to form a tough, heat resistant, semi-thermoplasticresin.

When para-phenylene diamine di-hydrochloride,

n 11 a H or meta-phenylene diamine di-hydrochloride,

or benzidine di-hydrochloride,

is added to the polymer formed from aniline and formaldehyde and themixture is heated to between 130 C. and 190 C.,'the aromatic diaminedi-hydrochloride cross links the resin chains and increases the strengthof the resin. When such a resin is used for the bond of a grindingwheel, I find that superior results in grinding can be achieved. Theinvention has particular utility when embodied in snagging wheels thepurpose of which is to clean off the fins, risers, cores and the likefrom rough castings and to smooth billets and the like prior to rolling.Snagging involves the removal of much metal and usually in snaggingoperations the desideratum is to remove metal as quickly as possiblewith a minimum amount of wheel wear.-

It is my belief that one of the improved results in grinding with wheelsmade according to the present invention is due to the release ofhydrogen chloride, hydrogen bromide or hydrogen iodide at the grindingline from the bond, caused by the generation of heat at this line, andthe reaction of the thus liberated acid halide with the metal of thework piece. It is my theory that the chips of metal clear themselvesfrom the abrasive grains more readily when their adhesion to theabrasive grains is broken by the presence of an acid. It should be notedthat the result is accomplished without the use of any liquid acid and,in fact, without any free acid excepting at the grinding line. At thispoint alone is the temperature high enough to liberate the acid from themolecule and cause its reaction with metal.

Considering now certain specific examples of the manufacture of grindingwheels in accordance with the present invention, I may proceed asfollows:

Example I Eight hundred and fifty-eight cubic centimeters of aniline isdissolved in eight liters of water containing nine and three-tenths molsof hydrochloric acid. To this is added seven hundred and fifty cubiccentimeters of formalin solution containing four-tenths gram offormaldehyde per cubic centimeter. After standing for one hour, aquantity of sodium hydroxide is added equivalent to the hydrochloricacid present. The precipitated resin is filtered, washed, dried andground to a fine powder. Into each ten pounds of this powdered resin Imix two and two-tenths pounds of para-phenylene diaminetil-hydrochloride.

Twenty-eight and one-tenth pounds of a porous, relatively pure grade offused alumina abrasive, #20 mesh grit size, is now wet with twenty-threehundredths of a pound of furfural. Five and nine-tenths pounds of theabove mixture of aniline formaldehyde resin and the diaminedi-hydrochloride are intimately mixed with the fused alumina wet withfurfural, spread in an eighteen inch mold with a five inch arbor. andhot pressed for one hour and a half at a temperature of 160 C. under apressure of three tons per square inch. The wheel is then stripped fromthe mold.

Para-phenylene diamine di-hydrochloride and the others heretoforementioned and other aromatic diamine di-hydrohalides (including thedihydrobromides and di-hydroiodides) have the property of giving ofihydrogen halide when heated to a temperature of the order of 500 C. Whencooled down well below that point, they no longer give up hydrogenhalide.

The furyl groups connecting benzene rings are derived from furfural (thealdehyde of furfurane) which is used to wet the abrasive grains. Whenfurfural is substituted in whole or in part for formaldehyde in theoriginal condensation process, a furyl group will be found replacing onehydrogen atom attached to the carbon atom of some of the methylenegroups connecting the amino groups to the opposite ring. In other words,the connection is through a furyl group. It will be seen that it is moreadvantageous to plasticize the abrasive grains with furfural becausethereby a number of additional linkages are provided in the polymericstructure, making it stronger.

Example II Thirty-seven pounds of #14 mesh fused alumina abrasive isplaced in a mixing pan and wet with five hundred and forty cubiccentimeters of furfural. To this are added nine pounds of the resin anddi-hydro-halogenated aromatic diamine of Example I and two pounds ofcryolite. The mixture, is spread in a sixteen inch mold with a six incharbor and hot pressed for two hours at a temperature of C. and under apressure of five hundred tons. Such a wheel will give as good a finishon stainless steel as a rubber wheel,; but is more durable. It may benoted at this point that cold pressing can be resorted toby reason ofthe plasticizing of the abrasive with furfural. However, the results arenot as satisfactory as when the hot pressing method is used.Furthermore, the addition of furfural definitely increases theplasticity and provides a better product made by the hot pressingmethod.

Example III Nineteen hundred and eighty grams of diamino diphenylmethane are dissolved in eight liters of water containing twenty mols ofhydrochloric acid. To this solution is added eight hundred cubiccentimeters of formalin solution containing four tenths gramformaldehyde per cubic centimeter. After standing for one hour aquantity of sodium hydroxide is added equivalent to the hydrochloricacid used. The precipitated resin is filtered, washed, dried, and groundto a fine powder.

Eight hundred and eight-five grams of #60 mesh fused alumina is mixeddry with one hundred and sixty grams of the above powdered resin andforty-nine grams of benzidine di-hydrochloride. This mixture is spreadin an eight inch mold and pressed at a temperature of 175 C. under apressure of one hundred and fifty tons for half an hour. Thisconstitutes a grinding wheel the resin bond of which is hard, tough andheat resistant. This bond likewise during grinding liberates hydrogenchloride at the grinding line.

Example I V One thousand and eighty grams of metaphenylene diamine isdissolved in eight liters of water containing twenty mols ofhydrochloric acid. To this solution is added six hundredcubiccentimeters of formalin, solution containing fourtenths gramformaldehyde per cubic centimeter. After standing for one hour, aquantity of sodium hydroxide is added equivalent to the hydro- Example VNine hundred and thirty grams of aniline and and two liters of watercontaining eleven mols of hydrochloric acid are mixed with six hundredand seventy cubic centimeters of furfural and I heated to 80 C.overnight. The solid mix resulting is ground and suspended in watercontaining sodium hydroxide equivalent to the hy-' drochloric acid used.After neutralization is complete, the powder is filtered, washed anddried.

Eight hundred and eighty-five grams of #60 mesh fused alumina is firstwet with thirty cubic centimeters of furfural. Then one hundred andsixty 'grams of the above powdered resin and twenty grams ofpara-phenylene diamine dihydrochloride are added. This mixture is spreadin an eight inch mold and pressed under a pressure of two hundred tons.It is then stripped from the mold and the green wheel is baked in anautoclave under a pressure of seven atmospheres at a temperaturegradually rising to 175 C. and maintained at this temperature forthreehours.

Example VI Ten hundred and seventy grams of meta toluidine are dissolvedin eight liters of water containing ten and two tenths mols ofphosphoric acid. To this solution is added seven hundred and fifty cubiccentimeters of formaldehyde solution containing four tenths of a gram offormaldehyde per cubic centimeter. After standing for one hour, aquantity of sodium hydroxide is added equivalent to the phosphoric acidused. The precipitated resin is filtered, washed, dried and ground to afine powder.

Eight hundred and eighty-five grams of 60 mesh fused alumina is firstwet with thirty cubic centimeters of furfural. Then one hundred andsixty grams of the above powdered resin and twenty grams ofmeta-phenylene diamine dihydrochloric are addedand mixed to produce adry granular mix. This mixture is spread in an two hundred tons at atemperature of 150 C. for one hour. It is then cooled and stripped fromthe mold, and is found to be a grinding wheel of superior 'quality. v

For the acid used in condensing the resin, besides hydrochloric andphosphoric, the following acids may also be used:

Hydriodic acid Tri-chloro acetic acid Di-chloro acetic acid Maleic acidOxalic acid Picric acid Sulphuric acid The requirement is that the acidshould be at least as strong as phosphoric acid to give the bestresults.

Every example of the invention constitutes abrasive grains bonded with ahalogenated primary amine-aldehyde resin. The halogen is derived fromthe aromatic dlamine dl-hydrohalides. In each of the examples thedi-hydrobromide and the di-hydroiodide, respectively, may be substitutedfor the di-hydrochloride and the same proportions can be used. Thefluorine compounds, however, are believed to be too stable. While I havementioned specific curing temperatures, it should be understood that anytemperature between 130 C. and 190 C. may be used for curing any of theresins with the aromatic amine di-hydrohalide.

It will thus be seen that there has been provided by this invention acomposition of matter, an article of manufacture, and an art in whichthe various objects hereinabove set forth together with many thoroughlypractical advantages are successfully achieved. As various possibleembodiments might be made of the mechanical features of the aboveinvention and as the art herein described might be varied in variousparts, all without departing from the scope of the invention, it is tobe understood that all matter hereinbefore set forth is to beinterpreted as illustrative and not in a limiting sense. I claim: r 1.An abrasive body comprising abrasive grains bonded with the condensationproduct of a molecular proportion of primary aromatic amine and betweenone and three molecular proportions of aldehyde selected from the groupconsisting of formaldehyde and furfural, condensed eight inch mold andpressed under a pressure of inthe presence of at least approximately onemolecular proportion of acid at least as strong as phosphoric acid andreacted by heating at resin curing temperatures with an aromatic aminedi-hydrolnalide, the halogen being selected from the group consisting ofchlorine, bromine and iodine.

2. An abrasive body comprising abrasive grains bonded with thecondensation product of one molecular proportion of aniline and betweenone and three molecular proportions of aldehyde selected from the groupconsisting of formaldehyde and furfural, condensed in the presence of atleast approximately one molecular proportion of acid at least as strongas phosphoric acid, andreacted by heating at resin curing temperatureswith an aromatic amine di-hydrohalide, the

halogen being selected from the group consisting of chlorine, bromineand iodine.

3. An abrasive body comprising abrasive grains bonded with thecondensation product of one molecular proportion of primary aromaticamine and between one and three molecular proportions of formaldehyde,condensed in the presence of at least approximately one molecularproportion of an acid at least as strong as phosphoric acid and reactedby heating at resin curing temperatures with an aromatic aminedi-hydrohalide, the halogen being selected from the group consisting ofchlorine, bromine and iodine.

4. An abrasive body comprising abrasive grains bonded with thecondensation product of one molecular proportionof aniline and betweenone and three molecular proportions oi aldehyde consisting at least inpart of formaldehyde, condensed in the presence of at leastapproximately one molecular proportion of acid at least as strong asphosphoric acid and reacted by heating at resin curing temperatures withan aromatic amine di-hydrohalide, the halogen being selected from thegroup consisting of chlorine, bromine and iodine.

5. An abrasive body according to claim 1 in which the condensationproduct has benzene rings linked together with furyl methylene groupsderived from furfural.

6. An abrasive body according to claim 2 in which the condensationproduct has benzene rings linked together with furyl methylene groupsderived from furfural. l

'7. An abrasive body according to claim 3 in which the condensationproduct has benzene rings linked together with furyl methylene groupsderived from furfural.

8. An abrasive body according to claim 4 in which the product hasbenzene rings linked together with furfural groups derived fromfurfural.

SAMUEL S. KISTLER.

